The present invention relates to containers for liquids, and more particularly to an ink cartridge for maintaining uniform pressure on an ink bag and for assisting in the dispensing of ink from the bag.
Ink jet printers utilize ink cartridges for storing and delivery of ink to a print head. Cartridges typically include an ink bag having walls made of a flexible sheet material. The sheet material is sealed such that the bag includes multiple seams. Excess stress on portions of the bag seams may cause a seam to rupture resulting in ink leaking from the bag and cartridge.
A need has thus arisen for an ink cartridge which evenly distributes the stress placed on seams of the ink bag to thereby reduce the risk of seam failure. A need has also arisen for an ink cartridge which generates a consistent amount of force on the ink during usage, especially when the bag ink supply within the cartridge becomes low.
In accordance with the present invention, an ink cartridge includes an ink bag for containing ink. The bag side walls are sealed together along the bottom to form a bottom seam and are sealed together along the bag sides to form side seams. The cartridge includes a housing having first and second side walls defining a cavity for receiving the bag. A first compressible foam sheet is disposed in the cavity between one of the side walls of the housing and one of the walls of the bag and adjacent the side seams. A second compressible foam sheet is disposed in the cavity between the other side wall of the housing and the other bag wall and adjacent the side seams. The foam sheets supply a uniform distribution of pressure along the side seams of the bag as ink is withdrawn from the bag and expand to assist in the uniform delivery of ink from the bag.